This invention relates to the manufacture of semiconductor devices and more particularly to the manufacture of semiconductor devices such as an integrated circuit in which a multilevel metallization system is utilized.
In the manufacture of integrated circuits particularly high density integrated circuits first, second and even third layers of metallization may be utilized to form all of the interconnects between the devices contained on a single chip. With each level of metallization the problem of metal continuity, i.e., step coverage, becomes more acute. The problem of step coverage occurs when a first layer of metallization, typically of aluminum, is deposited and the metallization formed into particular stripes or patterns. The stripes obviously form ridges across the surface of the semiconductor when a layer of insulating material is deposited across the ridge. If the sides of the ridge are substantially perpendicular the insulating material may not cover completely the sides of the ridge. Thus, when a further metallization layer is deposited this metallization may come directly in contact through holes in the insulation with the underlying metallization ridge. Obviously, contact between the two metallization layers will cause an electrical short. Even if the insulation material completely covers the metal, the deposition and subsequent patterning of the overlying metallization may become discontinuous as the metallization stripe crosses the underlying ridge, in effect "breaking" at the ridge and hence causing an electrical open.